The body system of an automobile uses for control an ECU (electronic control unit), which is generically called a body control module (BCM), connected to an I/O device via an exclusive line. The problem is, however, that the number of signal lines increases with the increasing systems to be controlled.
As a solution to this problem, Patent Document 1 discloses a method for controlling I/O devices, in which the state signal of each I/O device is accommodated in a multiplex transmission apparatus disposed in each of the parts of a vehicle, and the multiplex transmission apparatus is connected to a BCM via a multiplex transmission line.
Another method is disclosed in Patent Document 2, which is applied to a communication system using a multiplex transmission apparatus such as mentioned above. This method is designed to enable a BCM to detect a change in input data in a short amount of time, by transmitting the input data with the change to the BCM from the multiplex transmission apparatus when there is the change in the input data from an I/O device.